JP2016510399A - System and method for monitoring an estimated wheel speed of a vehicle using a transmission output shaft sensor - Google Patents

Abstract

A method and system for monitoring a determined wheel speed of a wheel is described. Three wheel speed values—representing measured wheel speeds for each different wheel—are received from different wheel speed sensors. An estimated wheel speed value for the fourth wheel is determined based on at least one of the three wheel speed values. A calculated wheel speed value is determined based on information received from the vehicle system. A failure condition is detected based on the deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel.

Description

Related applications
[0001] This application is based on the application of "SYSTEM AND METHOD FOR MONITORING AN ESTIMATED WHEEL SPEED OF A VEHICLE USING A TRANSMISSION OUTPUT SHAFFT SENSOR System and method for) claiming the benefit of US Provisional Patent Application No. 61 / 746,205, the entire contents of which are incorporated herein by reference.

  [0002] The present invention relates to systems and methods for monitoring individual wheel speeds of multi-wheeled vehicles such as passenger cars and trucks.

  [0003] Some modern vehicles include one or more electronic control units ("ECUs") that are configured to control various operations of the vehicle. For example, some vehicles include an Electronic Stability Control (“ESC”) system or other vehicle subsystem that controls the stability of the vehicle as it encounters various driving situations. The inventive arrangement described herein uses three wheel speed sensors to estimate the speed of the fourth wheel of the vehicle. Individual wheel speeds are then used to activate and control the operation of various vehicle subsystems (eg, ESC systems). In addition, the electronic control system calculates an estimated wheel speed based on information received from a transmission output shaft sensor (“TOSS”) and monitors the deviation between the estimated and calculated wheel speed.

  System and method for monitoring individual wheel speeds of a multi-wheel vehicle

  [0004] In one embodiment, the present invention provides a method of monitoring a determined wheel speed of a wheel. Three wheel speed values—representing measured wheel speeds for each different wheel—are received from different wheel speed sensors. An estimated wheel speed value for the fourth wheel is determined based on at least one of the three wheel speed values. A calculated wheel speed value is determined based on information received from the vehicle system. A fault condition is detected based on the deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel.

  [0005] In another embodiment, the present invention provides a wheel speed monitoring system that includes three wheel speed sensors, a processor, and a memory. The memory stores instructions that are executed by the processor to control the operation of the wheel speed monitoring system. The processor receives three wheel speed values-each from a different wheel speed sensor. Each of the three wheel speed values represents a measured wheel speed of a different wheel. The processor determines an estimated wheel speed value for the fourth wheel based on at least one of the three wheel speed values. The calculated wheel speed value is also determined based on information received from the vehicle system. A fault condition is detected based on the deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel.

  [0006] In yet another embodiment, the present invention provides a wheel speed monitoring system that includes a processor and a memory. The memory stores instructions that are executed by the processor to control the operation of the wheel speed monitoring system. The processor receives three wheel speed values-each from a different wheel speed sensor. Each of the three wheel speed values represents a measured wheel speed of a different wheel. The processor then determines a plurality of estimated wheel speed values for the fourth wheel of the vehicle. Each estimated wheel speed value is calculated according to a different estimation mechanism based on at least one of the three measured wheel speed values for the other wheels. The calculated wheel speed value is also obtained based on information received from the transmission output speed sensor. The processor calculates a plurality of deviation values-each based on one of the plurality of estimated wheel speed values and the calculated wheel speed value for the fourth wheel. The processor then compares each deviation value with a deviation threshold to determine the number of deviation values that exceed the deviation threshold among the plurality of deviation values. The processor concludes that a failure condition exists when the number of deviation values exceeding a deviation threshold value exceeds a deviation amount threshold value over a specified period among a plurality of deviation values.

  [0007] In some embodiments, the processor also determines whether an unstable driving situation exists and operates in the second monitoring mode if an unstable driving situation is detected. When operating in the second monitoring mode, the deviation threshold, the deviation threshold, and the specified period are all increased to compensate for deviations due to external forces acting on the vehicle during unstable driving conditions.

  [0008] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

[0009] FIG. 1 is a schematic diagram of a vehicle control system according to one embodiment. [0010] FIG. 5 is a flowchart of a method for monitoring estimated wheel speed and deviation between estimated wheel speed and calculated wheel speed. [0011] FIG. 5 is a flowchart of a method for comparing an estimated wheel speed with a calculated wheel speed during a stable driving situation. [0012] FIG. 5 is a flowchart of a method for comparing an estimated wheel speed with a calculated wheel speed during an unstable or dynamic driving situation.

  [0013] Before entering into a detailed description of embodiments of the present invention, the present invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. I want you to understand. The invention is capable of other embodiments and of being practiced or carried out in various ways.

  [0014] FIG. 1 illustrates a control system for a vehicle such as a four-wheeled passenger car or truck. An engine control unit 101 (“ECU”: Engine Control Unit) analyzes information such as vehicle performance variables and engine actuator settings and controls one or more vehicle / engine operations based on the received data. The ECU 101 includes a processor 103 and one or more non-transitory computer readable memory modules. In the example of FIG. 1, the ECU 101 includes a random access memory (“RAM”) module 105 and a read-only memory (“ROM”) module 107. The ECU 101 also includes an input / output interface 109 that transmits and receives data through a controller area network (“CAN”) bus 111. It should be understood that ECU 101 may include multiple processors, additional computer readable memory modules, multiple I / O interfaces, and / or additional components or modules (eg, hardware, software, or combinations thereof). .

  The processor 103 receives information from the I / O interface 111 and stores one or more stored in a memory module (also referred to as one or more “controllers”) of the ECU 101 such as a ROM 107. The information is processed by executing instructions for a software module (sometimes referred to as one or more “controllers”). The processor 103 stores information in and retrieves information from the RAM 105 (eg, information received from other vehicle subsystems or sensors through the CAN bus 111 and information generated by modules executed by the processor 103). The non-transitory computer readable memory module of ECU 101 includes volatile memory, non-volatile memory, or combinations thereof, and in various configurations may store operating system software, application / instruction data, and combinations thereof. .

  [0016] Various other vehicle subsystems are also connected to the CAN bus 111 and communicate with the engine control unit 101, various vehicle sensors, and other vehicle subsystems. For example, the braking subsystem 113 receives vehicle data and controls (symmetrically or asymmetrically) the braking pressure applied to each wheel of the vehicle. The steering subsystem 115 controls the steering angle applied to the front wheels of the vehicle based on the steering wheel position and other vehicle performance information. The drive train subsystem 117 controls the distribution of torque applied to the vehicle wheels. Each of these vehicle subsystems is connected to the CAN bus 111 and can exchange information with other devices connected to the CAN bus 111.

  Some vehicle sensors are also connected to the CAN bus 111. These vehicle sensors monitor various vehicle performance characteristics and provide information to other devices on the CAN bus 111. One such vehicle sensor is a transmission output speed sensor (“TOSS” sensor) 119. The TOSS sensor monitors the output speed of the transmission and determines the wheel speed of each individual wheel of the vehicle in combination with other information such as, for example, vehicle differential settings and data from the drivetrain subsystem 117. Provide information that can be used for The TOSS algorithm used to provide individual wheel speeds is known to those skilled in the art.

  [0018] Also connected to the CAN bus 111 is a series of wheel speed sensors 121, 123, 125, and 127 that are coupled to individual wheels 131, 133, 135, and 137, respectively. Each wheel speed sensor monitors the speed of the individual wheel and provides the CAN bus 111 with information indicating the wheel speed. The vehicle subsystem uses the wheel speed information for each individual wheel to modify the vehicle performance. For example, the engine control unit 101 determines that an unstable driving situation exists and activates an electronic stability control (“ESC”) program to distribute braking and torque to the wheels to restore vehicle stability. It's okay.

  [0019] However, in some situations, wheel speed information may not be available directly from sensors coupled to each of the four vehicle wheels. For example, one of the four wheel speed sensors (eg, the wheel speed sensor 121 corresponding to the left rear wheel 131 of the vehicle) may fail during operation of the vehicle and no longer provide data to the CAN bus 111. Alternatively, one of the four wheel speed sensors (for example, the wheel speed sensor 121 corresponding to the left rear wheel 131 of the vehicle) may be intentionally completely omitted from the vehicle for cost reduction. In such a situation, the ECU 101 estimates the wheel speed for the fourth wheel 133 based on the wheel speed sensor readings for the other three wheels 133, 135, and 137.

  [0020] The ECU 101 of FIG. 1 performs three simultaneous estimation calculations to determine the estimated wheel speed of the fourth vehicle wheel 131 based on the wheel speed sensor readings for the other three wheels 133, 135, and 137. Configured as follows. The ECU 101 first calculates the estimated speed of the fourth wheel 131 as an average of the other three wheel speeds:

_Where V _3wss is the estimated wheel speed of the fourth (left rear) wheel 131, V _FL is the measured wheel speed of the left front wheel 135, V _FR is the measured wheel speed of the right front wheel 137, and V _RR Is the measured wheel speed of the right rear wheel 133. Note that although the calculations presented in this example calculate the estimated wheel speed of the left rear wheel 131, it is possible to estimate the wheel speed of any other wheel of the vehicle using alternative configurations.

  Next, the ECU 101 calculates the estimated speed of the fourth wheel 131 based on the average measured wheel speed for the wheels on the other axles. For example, in order to estimate the wheel speed of the wheel on the rear vehicle axle, the ECU 101, based on the information from the left front wheel speed sensor 125 and the right front wheel speed sensor 127, according to the following formula, Calculate the average wheel speed of:

Where V _FA is the estimated wheel speed of the fourth wheel 131 based on the front axle average, V _FL is the measured wheel speed of the left front wheel 125, and V _FR is the measured wheel speed of the right front wheel 127.
[0022] Finally, the ECU 101 calculates the estimated speed of the fourth wheel 131 by equalizing the sum of the wheel speeds on each vehicle axle according to the following equation:
_{V RL_3wss = V FL + V FR} -V RR (3)
_Where V _{RL — 3wss} is the estimated wheel speed of the fourth wheel 131, V _FL is the measured wheel speed of the left front wheel 135, V _FR is the measured wheel speed of the right front wheel 137, and V _RR is the right rear wheel. 133 is the measured wheel speed.

  [0023] The ESC program can operate based on the estimated speed value for the fourth wheel calculated by any of the above equations (1), (2), or (3), or the average of the three estimated values. Alternatively, as described above, the TOSS sensor 119 provides information that can be used to calculate the wheel speed for each individual wheel (including the fourth sensorless wheel) based on the output of the vehicle transmission. As such, the ESC program can use wheel speed values calculated based on information from the TOSS sensor 119.

  [0024] However, neither the estimated wheel speed value nor the calculation based on the TOSS sensor provides a direct measurement of the wheel speed for the fourth wheel. In addition, due to error conditions at the TOSS sensor or elsewhere in the drive train, the wheel speed calculation may incorrectly represent the actual wheel speed of the fourth (sensorless) wheel. FIG. 2 monitors the speed value for the fourth wheel 131 calculated based on information from the TOSS sensor 119 and estimates the wheel based on the measured wheel speeds of the other four vehicle wheels 133, 135, and 137. A method for confirming the calculated speed value based on the speed value is illustrated.

  [0025] ECU 101 receives wheel speed sensor values from each of three existing / active wheel speed sensors 123, 125, and 127 (step 201). ECU 101 analyzes the signal quality from these sensors to determine if they provide a reliable indicator of measured wheel speed (step 203). If the signal quality is not acceptable (step 205), the ECU 101 disables the TOSS monitoring mechanism described later (step 207). On the other hand, if the signal quality is sufficient, the ECU 101 enables TOSS monitoring (step 209).

  [0026] If the driving situation is currently stable (eg, steady speed, flat road surface, no overturning) (step 211), the ECU 101 performs high speed mode monitoring and verifies the estimated wheel speed based on the TOSS output. (Step 213). On the other hand, when an unstable (or dynamic) driving situation is detected (step 211), the ECU 101 uses low-speed mode TOSS monitoring (step 217). In some configurations, the ECU 101 determines that an unstable / dynamic driving situation exists when the ESC program (or other vehicle stability program) is activated. Further, in some configurations, the ECU 101 may determine that the driving situation is so unstable that the wheel speed calculation cannot be accurately verified (step 215). Under such conditions, the ECU 101 disables TOSS monitoring until the driving situation is stabilized (step 207).

  [0027] FIG. 3 illustrates high-speed mode monitoring of wheel speed calculation based on the output of the TOSS sensor 119. In the high speed mode, during more stable driving situations, the wheel speed calculated based on the output of the TOSS sensor 119 is faster and more sensitive than when operating under unstable / dynamic driving conditions. It operates on the assumption that it can be confirmed. The ECU 101 first calculates three estimated values related to the speed of the fourth wheel based on the above-described equations (1), (2), and (3) (step 301). ECU 101 then calculates a deviation value for each estimated wheel speed value compared to the wheel speed value calculated based on TOSS sensor 119 (step 303) —a total of three deviation values (one for each wheel speed estimate). Is obtained. Each deviation value is calculated according to the following formula:

In the equation, λ is a deviation value, V _{RL_TOSS} is a wheel speed value for the left rear wheel based on the output of the TOSS sensor 119, and V _{RL_EST} is an estimated wheel speed value for the left rear wheel (the above formulas (1), ( 2) and calculated according to one of (3)).

  [0028] ECU 101 then compares each of the three deviation values to a "fast mode" deviation threshold (step 305). The ECU 101 tracks the time when at least two deviation values exceed the “high speed mode” deviation threshold (step 309), and if the deviation continues over the prescribed “high speed mode” time threshold (step 313), the ECU 101 A condition exists and it is determined that the wheel speed calculation for the fourth (sensorless) wheel is unreliable (step 313). If the deviation value exceeding the “high-speed mode” deviation threshold is one or less at any time (step 305), the ECU 101 resets the time counter (step 307).

  [0029] FIG. 4 illustrates low-speed mode monitoring of wheel speed calculation based on the output of the TOSS sensor 119. As mentioned above, “low speed mode” monitoring assumes that deviations due to external factors are more likely to occur during unstable / dynamic driving situations, and therefore deviations must be detected with lower sensitivity over a longer period of time. Is used during the unstable / dynamic driving situation by the ECU 101.

  [0030] "Low speed mode" monitoring begins by calculating three estimates for the speed of the fourth wheel based on equations (1), (2), and (3) above (step 401). . ECU 101 then calculates a deviation value for each estimated wheel speed value according to equation (4) above (step 403) —a total of three deviation values (one for each wheel speed estimation) are obtained. The ECU 101 compares each deviation value with a “low speed mode” deviation threshold (step 405) and tracks the time when all three deviation values exceed the “low speed mode” deviation threshold (step 409). If at least one of the deviation values falls below the “low speed mode” deviation threshold, the ECU 101 resets the timer (step 407). However, if the timer reaches the “low speed mode” time threshold (step 411), the ECU 101 determines that a fault condition exists and the wheel speed calculation for the fourth (sensorless) wheel is unreliable (step 413). .

  [0031] Although "low speed mode" monitoring is similar to "high speed mode" monitoring, there are some important differences. First, the “low speed mode” time threshold is longer than the “high speed mode” time threshold. Therefore, during the “low speed mode” monitoring, there must be a deviation over a longer period for the ECU 101 to declare a fault condition. Furthermore, the “low speed mode” deviation threshold is higher than the “high speed mode” deviation threshold. As such, in order for the ECU 101 to declare a failure state, the deviation between the estimated wheel speed value and the calculated value based on TOSS becomes larger. Finally, during “fast mode” monitoring, only two deviation values need to exceed the deviation threshold, while during “low speed mode” monitoring, all three deviation values must exceed the threshold. As described above, during unstable / dynamic driving situations, external factors are more susceptible to deviations between estimated and calculated wheel speed values. These differences between "high speed mode" and "low speed mode" monitoring are the difference between the estimated wheel speed value and the calculated wheel speed value based on TOSS in order for a fault condition to be declared during operation in "low speed mode" monitoring. Compensating for these external influences by requiring that deviations between them be more prominent and exist for a longer period of time.

  [0032] Accordingly, the present invention provides, among other things, a system and method for monitoring and verifying a calculated wheel speed of a particular wheel of a vehicle based on a deviation between the calculated wheel speed and a measured wheel speed of other vehicle wheels. I will provide a. Although the above examples all relate to estimating wheel speed values for the left rear wheel, it is noted that the methods and systems described herein can be applied to estimate and validate the wheel speed for any vehicle wheel. I want. Furthermore, while the above example describes three specific equations for using the measured wheel speed values for the three wheels to calculate the estimated wheel speed value for the fourth wheel, Can use different estimation mechanisms and can use more than four or less than two estimates. Various features and advantages of the invention are set forth in the following claims.

Claims (16)

A method of monitoring the determined wheel speed of a wheel,
Receiving a first wheel speed value indicative of a measured wheel speed of the first wheel of the vehicle from a first wheel speed sensor;
Receiving a second wheel speed value indicating a measured wheel speed of a second wheel of the vehicle from a second wheel speed sensor;
Receiving a third wheel speed value indicative of a measured wheel speed of a third wheel of the vehicle from a third wheel speed sensor;
Determining an estimated wheel speed value for a fourth wheel of the vehicle based on at least one of the first wheel speed value, the second wheel speed value, and the third wheel speed value;
Obtaining a calculated wheel speed value for the fourth wheel based on information received from the vehicle system;
Determining that a fault condition exists based on a deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel. Obtaining a calculated wheel speed value for the fourth wheel;
Receiving information from a transmission output speed sensor;
And determining the calculated wheel speed value based on the information from the transmission output speed sensor. Obtaining an estimated wheel speed value for the fourth wheel;
Calculating an average of the first wheel speed value, the second wheel speed value, and the third wheel speed value;
And setting the estimated wheel speed value for the fourth wheel as being the calculated average. Obtaining an estimated wheel speed value for the fourth wheel;
Calculating an average of the first wheel speed value and the second wheel speed value, wherein the first wheel and the second wheel are located at a front end of the vehicle; And the fourth wheel is located at the rear end of the vehicle;
And setting the estimated wheel speed value for the fourth wheel as the calculated average. Obtaining an estimated wheel speed value for the fourth wheel;
Subtracting the third wheel speed value from the sum of the first wheel speed value and the second wheel speed value, wherein the first wheel and the second wheel are at the front end of the vehicle. Located, wherein the third wheel and the fourth wheel are located at a rear end of the vehicle;
And setting the estimated wheel speed value for the fourth wheel as a result of the subtraction. Determining that a failure condition exists based on a deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel;
Calculating a deviation value based on the estimated wheel speed value and the calculated wheel speed value;
Comparing the deviation value with a deviation threshold;
And determining that a fault condition exists if the deviation value exceeds the deviation threshold over a specified period of time. Determining whether a stable driving situation exists;
Operating in a first monitoring mode when a stable operating condition exists;
Further operating in a second monitoring mode when an unstable driving situation exists,
Determining that a failure condition exists based on a deviation between the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel;
Calculating a deviation value based on the estimated wheel speed value and the calculated wheel speed value;
Comparing the deviation value with a first deviation threshold when operating in the first monitoring mode;
Comparing the deviation value with a second deviation threshold when operating in the second monitoring mode, wherein the second deviation threshold is greater than the first deviation threshold;
Determining that a fault condition exists when the deviation value exceeds the first deviation threshold over a first specified period during operation in the first monitoring mode;
Determining that a fault condition exists when the deviation value exceeds the second deviation threshold over a second prescribed period during operation in the second monitoring mode, wherein the second prescribed period is the The method of claim 1, comprising: steps longer than the first prescribed period. A wheel speed monitoring system,
A first wheel speed sensor;
A second wheel speed sensor;
A third wheel speed sensor;
A processor;
When executed by the processor, the wheel speed monitoring system
Receiving a first wheel speed value indicative of a measured wheel speed of the first wheel of the vehicle from the first wheel speed sensor;
Receiving a second wheel speed value indicative of a measured wheel speed of the second wheel of the vehicle from the second wheel speed sensor;
Receiving a third wheel speed value indicative of a measured wheel speed of the third wheel of the vehicle from the third wheel speed sensor;
Based on at least one of the first wheel speed value, the second wheel speed value, and the third wheel speed value, an estimated wheel speed value related to the fourth wheel of the vehicle is obtained,
Based on information received from the vehicle system, the calculated wheel speed value related to the fourth wheel is obtained, and the estimated wheel speed value related to the fourth wheel and the calculated wheel speed value related to the fourth wheel A wheel speed monitoring system comprising: a memory storing a command for determining that a fault condition exists based on a deviation between the two. If the instructions are executed by the processor, the wheel speed monitoring system
Receiving information from a transmission output speed sensor;
The wheel speed monitoring system according to claim 8, wherein the calculated wheel speed value related to the fourth wheel is obtained by obtaining a calculated wheel speed value based on the information from the transmission output speed sensor. If the instructions are executed by the processor, the wheel speed monitoring system
Calculating an average of the first wheel speed value, the second wheel speed value, and the third wheel speed value;
The wheel speed monitoring system according to claim 8, wherein the estimated wheel speed value related to the fourth wheel is obtained by setting the estimated wheel speed value related to the fourth wheel as the calculated average. If the instructions are executed by the processor, the wheel speed monitoring system
Calculating an average of the first wheel speed value and the second wheel speed value, wherein the first wheel and the second wheel are located at a front end of the vehicle; And the fourth wheel is located at the rear end of the vehicle;
The wheel speed monitoring system according to claim 8, wherein the estimated wheel speed value related to the fourth wheel is obtained by setting the estimated wheel speed value related to the fourth wheel as the calculated average. If the instructions are executed by the processor, the wheel speed monitoring system
Subtracting the third wheel speed value from the sum of the first wheel speed value and the second wheel speed value, wherein the first wheel and the second wheel are at the front end of the vehicle. And the third wheel and the fourth wheel are located at the rear end of the vehicle;
The wheel speed monitoring system according to claim 8, wherein the estimated wheel speed value related to the fourth wheel is obtained by setting the estimated wheel speed value related to the fourth wheel as a result of the subtraction. If the instructions are executed by the processor, the wheel speed monitoring system
Calculating a deviation value based on the estimated wheel speed value and the calculated wheel speed value;
Comparing the deviation value with a deviation threshold;
Determining that a failure condition exists when the deviation value exceeds the deviation threshold over a specified period, and calculating the estimated wheel speed value for the fourth wheel and the calculated wheel speed value for the fourth wheel; The wheel speed monitoring system according to claim 8, wherein a fault condition is determined to exist based on a deviation between the two. If the instructions are executed by the processor, further to the wheel speed monitoring system,
To determine if a stable driving situation exists,
Operate in the first monitoring mode when stable operating conditions exist, and operate in the second monitoring mode when unstable operating conditions exist,
If the instructions are executed by the processor, the wheel speed monitoring system
Calculating a deviation value based on the estimated wheel speed value and the calculated wheel speed value;
Comparing the deviation value with a first deviation threshold when operating in the first monitoring mode;
Comparing the deviation value with a second deviation threshold during operation in the second monitoring mode, wherein the second deviation threshold is greater than the first deviation threshold;
Determining that a fault condition exists when the deviation value exceeds the first deviation threshold over a first specified period during operation in the first monitoring mode;
Determining that a fault condition exists when the deviation value exceeds the second deviation threshold over a second prescribed period during operation in the second monitoring mode, wherein the second prescribed period is the It is determined that a failure condition exists based on a deviation between the estimated wheel speed value related to the fourth wheel and the calculated wheel speed value related to the fourth wheel due to being longer than the first specified period. The wheel speed monitoring system according to claim 8. A wheel speed monitoring system comprising a processor and a memory, wherein when the memory is executed by the processor, the wheel speed monitoring system includes:
Receiving a first wheel speed value indicative of a measured wheel speed of the first wheel of the vehicle from a first wheel speed sensor;
Receiving a second wheel speed value indicative of a measured wheel speed of the second wheel of the vehicle from a second wheel speed sensor;
Receiving a third wheel speed value indicative of a measured wheel speed of the third wheel of the vehicle from a third wheel speed sensor;
A plurality of estimated wheel speed values for the fourth wheel of the vehicle are obtained, and each estimated wheel speed value of the plurality of estimated wheel speed values is calculated from the first wheel speed value, the second wheel speed value, and Determined according to a different estimation mechanism based on at least one of the third wheel speed values;
Based on the information received from the transmission output speed sensor, the calculated wheel speed value for the fourth wheel is obtained,
Calculating a plurality of deviation values, each deviation value being based on one of the plurality of estimated wheel speed values and the calculated wheel speed value for the fourth wheel;
Each deviation value of the plurality of deviation values is compared with a deviation threshold;
When the number of deviation values exceeding the deviation threshold among the plurality of deviation values is obtained, and the number of deviation values exceeding the deviation threshold among the plurality of deviation values exceeds a deviation amount threshold over a specified period. A wheel speed monitoring system for storing a command for determining that a fault condition exists. If the instructions are executed by the processor, further to the wheel speed monitoring system,
To determine if an unstable driving situation exists,
If there is an unstable driving situation, operate in the second monitoring mode,
When operating in the second monitoring mode, each deviation value of the plurality of deviation values is compared with a second deviation threshold value, and the second deviation threshold value is larger than the first deviation threshold value,
Determining the number of deviation values exceeding the second deviation threshold value among the plurality of deviation values during operation in the second monitoring mode, and out of the plurality of deviation values during operation in the second monitoring mode. When the number of deviation values exceeding the second deviation threshold exceeds the second deviation amount threshold over a second specified period, it is determined that a fault condition exists, and the second deviation amount threshold is the deviation The wheel speed monitoring system according to claim 15, wherein the wheel speed monitoring system is greater than a quantity threshold and the second prescribed period is greater than the prescribed period.

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